1. Field of the Invention
The present invention relates to a PWM (pulse width modulation) signal demodulation method and, more particularly, to a method for obtaining the modulation factor of a signal modulated by a PWM circuit and demodulating the modulated signal based on the modulation factor obtained.
2. Description of the Prior Art
With signals modulated by a PWM circuit, their trailing edges in waveforms vary while their leading edges remain fixed. To demodulate any of such modulated signals (PWM signals) has conventionally required using an integrator to find the modulation factor thereof on which the demodulation process is based.
One disadvantage of the prior art demodulation method that uses the integrator is that when the carrier frequency (leading edge period in waveform) of the modulated signal varies, the level of the signal demodulated by the method also varies.
Another disadvantage of the prior art demodulation method is that if the varying width of the carrier frequency is significantly large, the width may exceed the linearity domain of the integrating characteristic of the integrator in use. This means that the integrator tends to lag behind in its integrating operation during the demodulation process.